Reticles, and methods of treating reticles, configuring reticles and using reticles

ABSTRACT

Some embodiments include methods of treating reticles to provide backside masking across regions of the reticle to compensate for problems occurring during photolithographic processing. The problems may be, for example, defects in the reticle, problems associated with deposition or development of photoresist, or problems associated with substrate topography. The masking may alter one or both of transmission of electromagnetic radiation through the masked regions, and polarization of electromagnetic radiation passed through the masked regions. Some embodiments include reticles having patterns along front sides for patterning electric magnetic radiation, and masks across portions of the backsides to at least partially block transmission of electromagnetic radiation through portions of the patterns.

TECHNICAL FIELD

Reticles, methods of treating reticles, methods of configuring reticles,and methods of using reticles.

BACKGROUND

Photolithography is commonly used during formation of integratedcircuits on semiconductor wafers. More specifically, a form of radiantenergy (such as, for example, ultraviolet light) is passed through aradiation-patterning tool and onto a radiation-sensitive material (suchas, for example, photoresist) associated with a semiconductor wafer. Theradiation-patterning tool can be referred to as a photomask or areticle. The term “photomask” traditionally is understood to refer tomasks which define a pattern for an entirety of a wafer, and the term“reticle” is traditionally understood to refer to a patterning toolwhich defines a pattern for only a portion of a wafer. However, theterms “photomask” (or more generally “mask”) and “reticle” arefrequently used interchangeably in modern parlance, so that either termcan refer to a radiation-patterning tool that encompasses either aportion or an entirety of a wafer. For purposes of interpreting thisdisclosure and the claims that follow, the terms “reticle” and“photomask” are utilized interchangeably to refer toradiation-patterning tools that define patterns across some or all of awafer.

Reticles contain light restrictive regions (for example, totally opaqueor attenuated/half toned regions) and light transmissive regions (forexample, totally transparent regions) formed in a desired pattern. Agrating pattern, for example, can be used to define parallel spacedconductive lines on a semiconductor wafer.

Photolithography initially comprises forming a layer ofradiation-sensitive material (such as, for example, photosensitiveresist material, which is commonly referred to as photoresist) over awafer. Subsequently, radiation is passed through the reticle onto thelayer of photoresist, and a pattern defined by the reticle istransferred onto the photoresist. The photoresist is then developed toremove either the exposed portions of photoresist for a positivephotoresist or the unexposed portions of the photoresist for a negativephotoresist. The remaining patterned photoresist can then be used as amask on the wafer during a subsequent semiconductor fabrication step,such as, for example, ion implantation or etching relative to materialson the wafer proximate the photoresist.

An example prior art photolithography process is described withreference to FIGS. 1-3.

FIG. 1 shows a reticle 10 comprising a base (or body) 12. A series ofradiation-altering structures 11, 13, 15 and 17 are provided over asurface of the body, and a series of regions (specifically gaps) 14, 16and 18 are between the radiation-altering structures. Theradiation-altering structures 11, 13, 15 and 17, together with the gaps14, 16 and 18 define a pattern imparted to radiation passing throughreticle 10. Although the pattern imparted to the radiation is defined bythe structures and gaps, the pattern may differ from the specificpattern of the structures and gaps due to interference effects occurringin the radiation as it passes through the reticle. Such interferenceeffects are accounted for in the design of the reticle.

The body 12 may comprise, consist essentially of, or consist of materialtransparent, or at least substantially transparent, to radiation passedthrough the reticle during photolithography; and may, for example,comprise, consist essentially of, or consist of quartz. Theradiation-altering structures 11, 13, 15 and 17 may comprise materialswhich block a significant percentage of electromagnetic radiation frompassing therethrough (for instance, chromium-containing materials),and/or may comprise materials which shift the phase of electromagneticradiation passing therethrough (for instance, molybdenum silicide). Theradiation-altering structures may comprise materials formed across asurface of base 12 (as shown) or may comprise patterns etched into base12 (for instance, may comprise grating patterns etched into base 12 toshift a phase of electromagnetic radiation passing through the base).

The structures 11, 13, 15 and 17 may define relatively opaque portionsof the reticle, and the gaps 14, 16 and 18 may define relativelytransparent portions of the reticle. The terms “relatively opaque” and“relatively transparent” are utilized to indicate regions which are moreopaque or transparent relative to one another, respectively, and mayinclude, but are not limited to, regions which are completely opaque orcompletely transparent, respectively. Together, the relatively opaqueregions and relatively transparent regions pattern radiation passingthrough the reticle.

The regions 14, 16 and 18 are shown to consist of unmodified locationsof base 12. In some application the regions are modified prior tophotolithography by, for example, forming materials within the regions,and/or by recessing at least portions of the regions into the base.

The base 12 has a pair of opposing sides 7 and 9. The pattern ofstructures 11, 13, 15 and 17, and regions 14, 16 and 18, is formed alongside 7. The patterned side 7 may be referred to as a front side of thereticle, and the opposing side 9 may be referred to as a backside of thereticle.

FIG. 2 shows an apparatus 20 utilizing reticle 10 for patterningradiation. Apparatus 20 contains a semiconductor substrate 22 having aradiation-sensitive material 26 over a base 24. The base may comprise,consist essentially of, or consist of monocrystalline silicon. Theradiation-sensitive material may comprise positive or negativephotoresist. The radiation-sensitive material may be particularlysensitive to one or more wavelengths of radiation, such as, for example,wavelengths shorter than 300 nanometers.

The terms “semiconductive substrate,” “semiconductor construction” and“semiconductor substrate” mean any construction comprisingsemiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials), and semiconductive materiallayers (either alone or in assemblies comprising other materials). Theterm “substrate” refers to any supporting structure, including, but notlimited to, the semiconductive substrates described above. Although base24 is shown to be homogenous, the base may comprise numerous layers insome applications. For instance, base 24 may contain one or more layersassociated with integrated circuit fabrication. In such applications,such layers may correspond to one or more of metal interconnect layers,barrier layers, diffusion layers, insulator layers, etc.

The semiconductor substrate 22 is provided beneath the front side 7 ofreticle 10. Electromagnetic radiation 28 is patterned by passing itthrough reticle 10. The radiation may comprise a plurality ofwavelengths, with one or more of the wavelengths being the predominatewavelengths utilized for patterning the radiation-sensitive material.The wavelengths predominately utilized for patterning theradiation-sensitive material may be referred to as the “primary”wavelengths utilized in the printing of a pattern into theradiation-sensitive material.

The patterned radiation impacts radiation-sensitive material 26 to printa pattern within the radiation-sensitive material. The printed patterncomprises exposed regions 30 and non-exposed regions 32. The exposed andnon-exposed regions are shown separated by dashed-line boundaries toassist in illustrating the exposed and non-exposed regions.

FIG. 3 shows semiconductor substrate 22 after development of theradiation-sensitive material 26 to remove the exposed regions 30selectively relative to the unexposed regions (alternatively, thedevelopment may remove the unexposed regions selectively relative to theexposed regions). The development forms a plurality of openings 34, 36and 38 extending through the radiation-sensitive material to theunderlying base 24. In subsequent processing, an etch may be conductedto extend the openings into the base.

In many semiconductor fabrication processes, it is desired to form alarge array of identical openings extending through aradiation-sensitive material. For instance, is often desired for memoryto comprise large arrays of identical structures. FIG. 3 shows a desiredresult in which the openings are uniformly created to the samedimensions as one another (in other words, in which the openings haveuniform critical dimensions across base 24). In practice, such desiredresult is often not achieved.

FIG. 4 illustrates an example problem that may occur during formation ofthe openings 34, 36 and 38. Specifically, FIG. 4 shows that opening 36has not entirely penetrated through the radiation-sensitive material 26.Such may be due to a problem with the substrate 24 (for instance, thesubstrate may not have a planar topography of the upper surface), aproblem with the radiation-sensitive material (for instance, theradiation-sensitive material may not have been formed to uniformthickness across the substrate), or a problem during the exposure ofFIG. 2 (for instance, one of the openings in the pattern on the reticlemay not have had appropriate dimension relative to the other openingsand/or the intensity of electromagnetic radiation through part of thereticle may not have been the same as the intensity through another partof reticle).

FIG. 5 illustrates another example problem that may occur duringformation of openings 34, 36 and 38. Specifically, the openings 34, 36and 38 are not uniform in critical dimension; with openings 34 and 38being shown to be wider than opening 36. Such problem may result from,for example, non-uniformity in dimensions of the openings in the patternon the reticle.

The same reticle and processing methods may be utilized for sequentialprocessing of numerous substrates. A problem that occurs on onesubstrate will frequently occur on all of the sister substratesprocessed with the same reticle and processing conditions. Accordingly,it is desired to develop procedures for curing photolithographicproblems before they are propagated to a large number of substrates.

Advances in semiconductor integrated circuit performance have typicallybeen accompanied by a simultaneous decrease in integrated circuit devicedimensions and a decrease in the dimensions of conductor elements whichconnect those integrated circuit devices. The demand for ever smallerintegrated circuit devices brings with it demands for ever decreasingdimensions of structural elements, and ever increasing requirements forprecision and accuracy in radiation patterning.

Control of critical dimension uniformity during photolithographicformation of openings may be of increasing importance as ever higherlevels of integration are sought for integrated circuit fabrication.Efforts have been made to improve critical dimension uniformity byimproving the reticles utilized for photolithography. One method is todarken a reticle by using a laser to damage quartz. The damaged quartzattenuates light passing through the reticle, which may inducebirefringence, and which may thereby affect critical dimension byreducing the degree of polarized light (in other words, by shifting aphase of the polarized light). This may be undesirable in someapplications.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagrammatic cross-sectional view of a prior art reticle.

FIG. 2 is a diagrammatic cross-sectional view of a prior art apparatusutilizing the reticle of FIG. 1 for patterning of a radiation-sensitivematerial associated with a semiconductor substrate.

FIG. 3 is a view of the semiconductor substrate of FIG. 2 shown at aprior art processing stage subsequent to that of FIG. 2.

FIG. 4 is a view of the semiconductor substrate of FIG. 2 shown at aprior art processing stage subsequent to that of FIG. 2 illustrating aprior art problem.

FIG. 5 is a view of the semiconductor substrate of FIG. 2 shown at aprior art processing stage subsequent to that of FIG. 2 illustratinganother prior art problem.

FIG. 6 is a diagrammatic cross-sectional view of an embodiment of areticle.

FIGS. 7 and 8 are a diagrammatic cross-sectional view, and top view,respectively, of another embodiment of a reticle. The cross-section ofFIG. 7 is along the line 7-7 of FIG. 8.

FIG. 9 is a diagrammatic cross-sectional view of another embodiment of areticle.

FIGS. 10-12 are top views of a reticle at various processing stages ofan embodiment.

FIGS. 13 and 14 are top views of a reticle at various processing stagesof another embodiment.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Some embodiments include methods of improving critical dimensionuniformity of openings formed during photolithography. Such improvementmay include provision of halftone and/or bulk attenuating structures onreticle backsides.

Some embodiments include deposition of a material across part of thebackside of a reticle to attenuate incoming light to improve criticaldimension uniformity. The deposition may include laser assistance, andmay be, for example, laser-enhanced chemical vapor deposition. Thedeposited material may be formed in any desired pattern. In someembodiments, the material may comprise chrome-containing dots (or otherchrome-containing elements) on a pitch which changes transmission, andin other embodiments may comprise a complete monolayer (or otherthickness layer) across a substantial portion of a pattern to blockutilization of that portion of the pattern during a photolithographicprocess.

In some embodiments, the critical dimensions of a pattern on a reticleare measured to create a map of the critical dimension uniformity, andthen a map for correction is calculated and the treatment of thebackside conducted. In other embodiments, the critical dimensions of aphotolithographically-formed pattern on a substrate are measured tocreate a map of the critical dimension uniformity, and then a map forcorrection is calculated and the treatment of the backside of thereticle utilized for the photolithography is conducted.

In embodiments in which masks are formed on reticle backsides, the masksmay be removed in subsequent processing so that the same reticles may beused for forming different types of patterns on different substrates.

In some embodiments, a polarizing material or pattern is provided on thebackside of the reticle in addition to, or alternatively to, atransmission-blocking (in other words, attenuating) mask. A polarizingmaterial may be tailored to address polarization issues (for instance,birefringence) in a reticle.

The attenuating masks and polarizing treatments may be utilized toproduce pixel and/or zone-based corrections for attenuation, and/orpolarization. The attenuating masks and polarizing treatments mayimprove critical dimension uniformity produced with a photolithographicprocess and/or may improve polarization purity of radiation passingthrough a reticle during a photolithographic process.

An example embodiment reticle 40 is shown in FIG. 6. Similar number willbe used to describe reticle 40 as is utilized to describe the prior artreticle of FIG. 1, where appropriate.

The reticle 40 comprises the base 12 having the front side 7 and theopposing backside 9. The reticle 40 also comprises a pattern over thefront side 7, with such pattern including structures 11, 13, 15 and 17,and the regions 14, 16 and 18 between the structures. In contrast to theprior art reticle of FIG. 1, the reticle of FIG. 6 comprises a patternedmask 42 on the backside 9 of the reticle. The mask 42 comprises a firstportion 44 over region 14, and a second portion 46 over region 18.

In some embodiments, a prior art reticle may be utilized to form asubstrate having the problem shown in FIG. 4. The problem may beidentified as an undesired feature within the gap 36, with suchundesired feature corresponding to a film of resist 26 remaining withingap 36 after development of the resist. The remaining film may be due toone or more of various problems associated with the reticle or with thephotolithographic process. For instance, the reticle may have highertransparency through regions which pattern gaps 34 and 38 than throughthe region which patterns gap 36; and/or the resist 26 may be thickerover the region where gap 36 is formed then over the regions where gaps34 and 38 are formed. Problems due to defects in the reticle, either dueto materials in the reticle or due to problems with the pattern on areticle, may be considered to be due to characteristics of the reticle.Problems due to formation of the photoresist or chemical development ofthe photoresist may be considered to be due to attributes other thancharacteristics of the reticle.

Once the undesired feature is identified as part of thephotolithographically patterned substrate, the reticle may be treatedwith the mask shown in FIG. 6 to at least diminish, and in someembodiments entirely eliminate, similar undesired features fromoccurring in additional substrates photolithographically patterned usingthe reticle.

The masking material 42 may be a material of suitable opacity formed tosuitable thickness to reduce transmission of electromagnetic radiationthrough features 14 and 18 by any desired amount. For instance, the maskmay reduce transmission by from about one percent to at least about 90percent, and may for example, reduce transmission by at least about 10percent or at least about 50 percent. The material 42 may comprise asingle composition, or may comprise multiple compositions. Although thematerial 42 is shown to be homogeneous, in other embodiments thematerial may comprise multiple discrete layers. In some embodiments,material 42 may comprise, consist essentially of, or consist of one ormore of aluminum, chromium, gold, molybdenum, platinum and tungsten. Inother embodiments, material 42 may comprise other materials. In someembodiments, material 42 may comprise a composition which shifts phase(in other words, changes polarization) of electromagnetic radiationpassing therethrough, with an example composition being molybdenumsilicide. Material 42 may thus, for example, comprise, consistessentially of, or consist of molybdenum silicide. The molybdenumsilicide may reduce transmission of electromagnetic radiation inaddition to shifting a phase of the electromagnetic radiation.

The masking material 42 may be formed by any suitable process including,for example, chemical vapor deposition (CVD), atomic layer deposition(ALD) and/or physical vapor deposition (PVD). In some embodiments, thematerial may be formed utilizing a laser-assisted process. Suchlaser-assisted process may be a laser-assisted deposition process inwhich a precursor is exposed to laser-emitted radiation to form adeposit from the precursor in a desired pattern across the backside ofthe reticle. Alternatively, the laser-assisted process may be aconventional deposition process which forms material across a largeregion of the backside (or, in some embodiments, an entirety of thebackside), and in which laser-emitted radiation is utilized toobliterate some of the deposited material to form a desired pattern fromthe material on the backside.

An example laser-induced chemical vapor deposition (LICVD) process is asfollows. A reticle is enclosed in a reaction chamber with anorganometallic compound which includes a metal to be deposited (forexample, trimethyl-aluminum may be utilized to deposit aluminum). Afocused laser is trained at a point of the reticle backside. The laserheats a localized area of the reticle backside. The heat causes nearbyorganometallic molecules to thermally decompose and deposit metal on theheated area.

Another example LICVD process is a photolytic process in which anorganometallic molecule is photochemically decomposed at or near areticle backside surface utilizing a laser operating at a wavelengthcorresponding to a photon energy which exceeds a chemical bond energy ofthe organometallic molecule. A photolytic process may have a lineardependence on laser light intensity. A number of separatemolecule-photon interactions may be utilized to break a number of bondsin order to release elemental metal for deposition. A portion of thephoton energy which exceeds a particular molecular bond energy mayinitially be converted to vibrational energy of the organometallicmolecule, and subsequently be dissipated to surrounding gas molecules asheat. The photolytic process may thus have some inefficiency relative tothe thermal process in that excess energy may not contribute toadditional bond-breaking interactions.

In some embodiments, the laser may be a mode-locked titanium-dopedsapphire (Ti:Sapphire) laser. The mode-locked Ti:Sapphire laser outputmay be characterized by a pulse time (which may be characterized by afull width half max value) of less than or equal to one picosecond (forinstance, less than or equal to 125 femptoseconds). An advantage ofusing short pulse light may be that if the pulse rate is maintainedsufficiently low, high intensity light may be obtained withoutadditional heating. It may be advantageous to use optical radiationabove deep ultraviolet (in other words, above 350 nanometers) to allowfor use of non-deep ultraviolet optical components. For manyapplications, wavelengths above deep ultraviolet will have sufficientresolution. If higher resolution is desired, wavelengths within the deepultraviolet may be utilized.

The vapor pressures of donor compounds (specifically, organometalliccompounds in some embodiments) may be at least about one millitorr, andin some embodiments maybe at least about 10 millitorr. Vapor pressuresof donor compounds may be temperature dependent. The desired donor vaporpressures may be selected to obtain a desired high rate of evaporationof the donor compounds, to ultimately provide a reasonable rate ofdelivery of the donor compounds to a reticle which is to be treated.Some donor compounds which may be acceptable for some embodimentsinclude, for example, chromium hexacarbonyl (which has a vapor pressureof from 200 millitorr to 300 millitorr at room temperature), molybdenumhexacarbonyl (which has a vapor pressure of from 100 millitorr to 200millitorr at room temperature), tungsten hexacarbonyl (which has a vaporpressure of from 20 millitorr to 100 millitorr at room temperature), anddimethyl-gold-trifluoro-acetylacetonate (which has a vapor pressure ofabout 100 millitorr at about 25° C.). Other example donor compoundsinclude aluminum hexafluoroacetylacetonate and platinumhexafluoroacetylacetonate.

FIGS. 7 and 8 show another example modification which may be made to thebackside of a reticle to correct for defects occurring in aphotolithographic process. In referring to FIGS. 7 and 8, similarnumbering will be used as is utilized above in describing FIGS. 1-6,where appropriate.

FIGS. 7 and 8 show a reticle 50 comprising the base 12 having the frontside 7 and the backside 9. The reticle 50 also comprises a pattern overthe front side 7; with such pattern containing structures 11, 13, 15 and17, together with regions 14, 16 and 18 between the structures.

The reticle 50 further comprises a pair of grating patterns 52 and 54 onthe backside 9 of the reticle. Grating pattern 52 is over region 14 ofthe patterned front side of the reticle, and grating pattern 54 is overregion 18 of the patterned front side of the reticle. The gratingpatterns may shift polarization of the electromagnetic radiation passingthrough features 14 and 18 relative to the polarization of radiationpassing through feature 16. Such can modify the radiation patternproduced by the reticle (for instance, the pattern produced duringprocessing of the type shown in FIG. 2), which may alleviate, or eveneliminate, some types of defects. The shift in phase may alter thecritical dimensions of an opening produced by radiation passing throughthe patterns of the reticle, which may alleviate problems of the typeshown in FIG. 5. Thus, uniformity of critical dimensions ofphotolithographically formed openings may be improved.

Other methods of shifting polarization may be used in addition to, oralternatively to, the grating pattern of FIGS. 7 and 8. For instance,phase shifting material may be formed over the backside 9 as a patternedmask, with exemplary phase shifting material being molybdenum silicide.

In some embodiments, the backside masks (for instance, the masksdescribed with reference to FIG. 6) may be combined with the backsidegrating patterns (for instance, the grating patterns described withreference to FIGS. 7 and 8) to simultaneously provide correction formultiple types of defects. For example, if a photolithographic processhas both problems of the type shown in FIG. 4 and problems of the typeshown in FIG. 5, the combination of masks and grating patterns maysimultaneously alleviate, or in some embodiments eliminate, both typesof problems.

FIG. 9 shows another example modification which may be made to thebackside of a reticle to correct for defects occurring in aphotolithographic process. In referring to FIG. 9, similar numberingwill be used as is utilized above in describing FIGS. 1-8, whereappropriate.

FIG. 9 shows a reticle 60 comprising the base 12 having the front side 7and the backside 9. The reticle 60 also comprises a pattern over thefront side 7; with such pattern containing structures 11, 13, 15 and 17,and the regions 14, 16 and 18 between the structures. The reticle 60additionally comprises a patterned mask 62 on the backside 9 of thereticle. The mask 62 comprises a portion over region 14, and comprisesanother portion over region 18.

The mask 62 is shown to comprise two discrete layers 64 and 66. Thelayers 64 and 66 may individually comprise any suitable compositions,and may, for example, comprise, consist essentially of, or consist ofone or more of aluminum, chromium, gold, molybdenum, platinum andtungsten. In some embodiments, one of the layers shifts phase ofelectromagnetic radiation passing therethrough, and the other reducestransmission of the radiation. For instance, layer 64 may consist ofmolybdenum silicide, and layer 66 may consist of a chromium-containingmaterial. The combined layers 64 and 66 may thus simultaneouslyalleviate, or in some embodiments eliminate, both the type of problemshown in prior art FIG. 4, and the type of problem shown in prior artFIG. 5.

The embodiments of FIGS. 6-9 illustrate applications in which maskingmaterial is provided over a backside of a reticle to correct for defectsin a photolithographic process. In other embodiments, masking materialmay be removably formed on the backside of a reticle to enable the samereticle to be utilized for printing multiple different layouts.Specifically, a reticle may be formed to have a pattern which includestwo or more different layouts which are desired to be printed indifferent photolithographic processes. Part of the pattern may be maskedso that one layout is printed; and then either the entire pattern isprinted for a different layout, or a different part of the pattern ismasked so that an alternate layout may be printed. Example embodimentsin which removable masking is applied to a reticle backside aredescribed with reference to FIGS. 10-14.

Referring to FIG. 10, a reticle 70 is illustrated. The reticle comprisesthe base 12 discussed above with reference to FIGS. 1-9. The base wouldcomprise a front side and backside, but in the view of FIG. 10 only thebackside 9 is visible. Specifically, FIG. 10 is a view of the reticlelooking down on the backside. A pattern 74 is formed on the front side,and such pattern is diagrammatically illustrated in dashed-line view inFIG. 10. The dashed-line view indicates that the pattern is under base12 relative to the view of FIG. 10.

The pattern is shown to comprise five primary sub-patterns 76, 78, 80,82 and 84. The sub-patterns are illustrated as blocks, and some of thesub-patterns are shown to overlap with one another (specifically,sub-pattern 80 overlaps with the sub-patterns 76, 78, 82 and 84). Thesub-patterns correspond to zones of the overall pattern. The individualzones may include any number of numerous specific features which are tobe transferred to a substrate during a photolithographic process. Forinstance, one or more of the zones may include only patternscorresponding to a single feature, or very few features (for instance,such zones may pattern specific sensors, or specific logic elements);and one or more of the zones may include patterns corresponding tothousands, or even millions of features (for instance, such zones maypattern repeating units of a memory array).

The zones may be considered to be separate patterns tailored forseparate applications. In some embodiments, it may be desired to use thezones to print a different arrangement of features on some substratesthan on other substrates. For instance, some of the zones may correspondto printed features which are proprietary for one customer, whereasothers of the zones may correspond to printed features which may beproduced for numerous customers. In such applications, it may be desiredto block the zone corresponding to the proprietary printed features whenprinting substrates for most customers, and then to unblock such zonewhen printing substrates for the customer that owns the proprietaryinformation. As another example, one or more of the zones may correspondto a sensor or other feature that a first set of customers desire,others of the zones may correspond to features that a second set ofcustomers desire; and yet others of the zones may correspond to featuresthat both the first and second sets of customers desire. In suchapplications, it may be desired to block one set of zones when printingsubstrates for the first set of customers, and to then unblock the firstset of zones and block a second set of zones when printing substratesfor the second set of customers.

The reticle of FIG. 10 comprises symmetry. Specifically, the shownreticle comprises mirror symmetry along a vertical plane designated bydashed-line 71, and comprises additional mirror symmetry along ahorizontal plane designated by dashed-line 73. In other embodiments, thereticle may be asymmetric.

FIGS. 11 and 12 illustrate example masks that may be used to block oneor more of the zones. Specifically, FIG. 11 shows a mask 90 patterned toblock zone 80. The mask 90 may comprise one or more compositionssuitable to block 99 percent or more of the transmission ofelectromagnetic radiation through zone 80; and may, for example,comprise, consist essentially of, or consist of one or more of aluminum,chromium, gold, molybdenum, platinum and tungsten. The mask 90 may blockall electromagnetic radiation, or may selectively block at least theprimary wavelengths of electromagnetic radiation utilized during theprinting. For instance, if the only electromagnetic radiation which canprint a particular radiation-sensitive material during aphotolithographic process is radiation having a wavelength in theultraviolet range or shorter, the mask may comprise a material whichblocks electromagnetic radiation having wavelengths in the ultravioletrange or shorter, but which lets some other wavelengths of radiationpass. The passing of the other wavelengths of radiation through the maskwill not detrimentally affect the photolithographic process since theydon't print the radiation-sensitive material.

The mask may be removably applied to the backside of the reticle, andmay be applied with any of the methods discussed above with reference toapplication of the masking material 42 of FIG. 6.

The mask 90 is substantially symmetric relative to the symmetry thereticle, and specifically comprises symmetry along the mirror planes 71and 73. The mask is referred to as being “substantially” symmetricrelative to the symmetry of the reticle to indicate that the mask issymmetric within limitations of fabrication, which may include, but isnot limited to, embodiments which the mask is exactly symmetric relativeto the symmetry of the reticle.

Referring to FIG. 12, mask 90 is removed and replaced with a patternedmask 92. The mask 90 may be removed with any suitable method. Forinstance, the mask may be removed with an etch, with laser-assistedobliteration, and/or with a polishing method. In an example embodiment,the mask may consist of a chromium-containing material, and may beremoved with an etch comprising oxygen and chlorine.

Mask 92 is provided over multiple non-contiguous locations of thereticle, and specifically is provided over zones 76, 78, 82 and 84. Themask 92 may comprise one or more compositions suitable to block 99percent or more of the transmission through zones 76, 78, 82 and 84; andmay, for example, comprise, consist essentially of, or consist of one ormore of aluminum, chromium, gold, molybdenum, platinum and tungsten.

Mask 92 is, like mask 90, substantially symmetric relative to thesymmetry of the reticle.

The mask 92 may be removably applied to the backside of the reticle, andmay be applied with any of the methods discussed above with reference toapplication of the masking material 42 of FIG. 6.

In subsequent processing, mask 92 may be removed and mask 90 reappliedso that reticle 70 may be alternately used for printing two differenttypes of patterns. In other processing, reticle 70 may be used with nomask applied, so that all of zones 76, 78, 80, 82 and 84 may be printed.In yet other processing, a mask may be provided to block othercombinations of zones 76, 78, 80, 82 and 84 besides the combinationsspecifically shown in FIGS. 11 and 12. Such other masks may beasymmetric relative to the reticle and may be provided over contiguouslocations of the reticle, or over multiple non-contiguous locations ofthe reticle.

FIGS. 13 and 14 illustrate another example embodiment in which aremovable mask may be provided across a backside of a reticle toselectively block some portions of the reticle during photolithographicprinting.

Referring to FIG. 13, a reticle 100 is illustrated. The reticlecomprises the base 12 discussed above with reference to FIGS. 1-9. Thebase would comprise a front side and backside, but in the view of FIG.13 only the backside 9 is visible. Specifically, FIG. 13 is a view ofthe reticle looking down on the backside. A pattern 102 is formed on thefront side, and such pattern is diagrammatically illustrated indashed-line view in FIG. 13. The dashed-line view indicates that thepattern is under base 12 relative to the view of FIG. 13.

The pattern is shown to comprise nine primary sub-patterns 104, 106,108, 110, 112, 114, 116, 118 and 120. The sub-patterns are illustratedas blocks, and none of the sub-patterns overlap with one another. Thesub-patterns correspond to zones of the overall pattern. The individualzones may include any number of numerous specific features which are tobe transferred to a substrate during a photolithographic process. Forinstance, one or more of the zones may include only patternscorresponding to a single feature, or very few features; and one or moreof the zones may include patterns corresponding to thousands, or evenmillions of features. The zones are shown to be approximately the samesize as one another, but in other embodiments the zones could havesubstantial variation in size relative to one another.

The reticle of FIG. 13 comprises symmetry. Specifically, the shownreticle comprises mirror symmetry along a vertical plane designated bydashed-line 101, and comprises additional mirror symmetry along ahorizontal plane designated by dashed-line 103. In other embodiments,the reticle may be asymmetric.

The reticle may be utilized to print a pattern by passing radiationthrough all of the shown zones of pattern 102. In subsequent processing,a mask may be provided to block one or more of the zones prior toprinting with others of the zones. For instance, FIG. 14 such shows amask 122 patterned to block zone 116. The mask 122 may comprise one ormore compositions suitable to block 99 percent or more of thetransmission of electromagnetic radiation through zone 116; and may, forexample, comprise, consist essentially of, or consist of one or more ofaluminum, chromium, gold, molybdenum, platinum and tungsten. The mask122 may block all electromagnetic radiation, or may selectively block atleast the primary wavelengths of electromagnetic radiation utilizedduring the printing.

The mask 122 may be removably applied to the backside of the reticle,and may be applied with any of the methods discussed above withreference to application of the masking material 42 of FIG. 6. The mask122 is asymmetric relative to the symmetry the reticle, and specificallylacks symmetry along the mirror planes 71 and 73.

Radiation may be passed through zones 104, 106, 108, 110, 112, 114, 118and 120 while the mask blocks zone 116 to print a pattern in aradiation-sensitive material. Subsequently, mask 122 may be removed, andeither other masks applied or reticle 100 used without masks to printother patterns.

Some of the embodiments described herein may advantageously enableasymmetric masks to be removably applied to reticles. In conventionalprocessing, it is difficult to asymmetrically modify a reticle, and anymodifications made tend to permanently alter the reticle. Among otheradvantages of at least some embodiments are that areas of a reticleaffected by treatment may be accurately controlled (to within a fewmicrons, or possibly to even tighter tolerances), the birefringence of areticle is not affected unless such is desired, and there is an abilityto induce selective polarization on particular areas of a reticle.Further, some embodiments may utilize completely reversible masking,which may enable the same reticle to be utilized for printing numerousdifferent patterns.

In compliance with the statute, the subject matter disclosed herein hasbeen described in language more or less specific as to structural andmethodical features. It is to be understood, however, that the claimsare not limited to the specific features shown and described, since themeans herein disclosed comprise example embodiments. The claims are thusto be afforded full scope as literally worded, and to be appropriatelyinterpreted in accordance with the doctrine of equivalents.

1. A method of treating a reticle, comprising: identifying regions ofthe reticle that are initiating undesired features in a substratephotolithographically patterned using the reticle, the reticle having apatterned front side and a backside in opposing relation to the frontside; and forming a mask across a portion of the backside to at leastdiminish the undesired features in additional substratesphotolithographically patterned using the reticle.
 2. The method ofclaim 1 wherein the mask is formed utilizing a laser-assisted process.3. The method of claim 1 wherein the mask is formed utilizing alaser-assisted deposition process.
 4. The method of claim 1 whereinforming the mask comprises: depositing at least one material across atleast a portion of the backside of the reticle; and obliterating some ofthe deposited material with a laser to pattern the deposited material.5. The method of claim 1 wherein the mask is provided over multiplenon-contiguous locations of the reticle.
 6. The method of claim 5wherein the mask is asymmetric relative to the reticle.
 7. The method ofclaim 5 wherein the mask is substantially symmetric relative to thereticle.
 8. The method of claim 1 wherein the mask eliminates theundesired features in the additional substrates.
 9. The method of claim1 wherein the undesired features result, at least in part, from one ormore characteristics of the reticle.
 10. The method of claim 1 whereinthe undesired features result from defects in the uniformity of thepattern of the front side of the reticle.
 11. The method of claim 1wherein the undesired features result, at least in part, from one ormore attributes other than characteristics of the reticle.
 12. Themethod of claim 1 wherein the mask reduces transmission ofelectromagnetic radiation through the pattern on the front side of thereticle.
 13. The method of claim 12 wherein the mask reduces thetransmission by at least about 1%.
 14. The method of claim 12 whereinthe mask reduces the transmission by at least about 10%.
 15. The methodof claim 12 wherein the mask reduces the transmission by at least about50%.
 16. The method of claim 12 wherein the mask reduces thetransmission by at least about 90%.
 17. The method of claim 1 whereinthe mask changes polarization of electromagnetic radiation.
 18. Themethod of claim 17 wherein the mask includes at least one grating. 19.The method of claim 17 wherein the mask includes molybdenum silicide.20. The method of claim 1 wherein the mask reduces transmission ofelectromagnetic radiation through the pattern on the front side of thereticle and changes polarization of the electromagnetic radiation. 21.The method of claim 20 wherein the mask reduces the transmission by atleast about 1%.
 22. The method of claim 20 wherein the mask reduces thetransmission by at least about 10%.
 23. A method of configuring areticle for multiple applications, comprising: forming the reticle tohave multiple patterns tailored for multiple different applications; thereticle having a front side and a backside, the patterns being formedalong the front side; and removably applying masking material across thebackside of the reticle to selectively have one or more of the patternsexposed during some photolithographic processes and blocked during otherphotolithographic processes.
 24. The method of claim 23 wherein at leasttwo of the patterns overlap with one another.
 25. The method of claim 23wherein none of the patterns overlap with one another.
 26. The method ofclaim 23 wherein the masking material comprises one or more of aluminum,chromium, gold, molybdenum, platinum and tungsten.
 27. A method offorming and using a reticle, comprising: forming the reticle to have anoverall pattern that comprises at least two sub-patterns; one of thesub-patterns being a first sub-pattern and the other being a secondsub-pattern; the reticle having a front side and a backside, and theoverall pattern being formed along the front side; using the reticleduring photolithographic patterning of a first set of substrates, thephotolithographic patterning using at least one primary wavelength ofelectromagnetic radiation that is passed through both the first andsecond sub-patterns; forming a mask across a portion of the backside ofthe reticle to block transmission of the at least one primary wavelengthof electromagnetic radiation through the first sub-pattern; and whilethe mask is across the portion of the backside of the reticle, using thereticle during photolithographic patterning of a second set ofsubstrates.
 28. The method of claim 27 wherein the first set ofsubstrates is photolithographically patterned before the second set ofsubstrates is photolithographically patterned.
 29. The method of claim27 wherein the first set of substrates is photolithographicallypatterned after the second set of substrates is photolithographicallypatterned.
 30. The method of claim 27 wherein the mask comprises one ormore of aluminum, chromium, gold, molybdenum, platinum and tungsten. 31.The method of claim 27 further comprising, after the photolithographicpatterning of the second set of substrates: stripping the mask; andusing the reticle for patterning a third set substrates.
 32. The methodof claim 27 wherein the mask is a first mask, wherein the blockedportion of the reticle is a first portion, and further comprising, afterthe photolithographic patterning of the second set of substrates:stripping the first mask; forming a second mask across a second portionof the backside of the reticle to block transmission of the at least oneprimary wavelength of electromagnetic radiation through the secondsub-pattern and while the second mask is across the second portion ofthe reticle, using the reticle for patterning a third set substrates.33. A reticle, comprising: a front side; a backside, a pattern along thefront side configured for patterning electromagnetic radiation; and amask across a portion of the backside to at least partially blocktransmission of the electromagnetic radiation through a portion of thepattern.
 34. The reticle of claim 33 wherein the mask only partiallyblocks transmission of the electromagnetic radiation through the portionof the pattern.
 35. The reticle of claim 33 wherein the mask entirelyblocks transmission of the electromagnetic radiation through the portionof the pattern.
 36. The reticle of claim 33 wherein the mask comprisesone or more of aluminum, chromium, gold, molybdenum, platinum andtungsten.
 37. The reticle of claim 33 wherein the mask comprisesmolybdenum silicide.